Q314752: FIX: adLockBatchOptimistic Slows Down VFP OLE DB Provider

Article: Q314752
Product(s): Microsoft FoxPro
Version(s): 7.0
Operating System(s): 
Keyword(s): kbGrpDSFox kbDSupport kbCodeSnippet kbvfp700 _IK283
Last Modified: 27-FEB-2002

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 7.0 
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SYMPTOMS
========

If you use the Visual FoxPro 7.0 OLE DB Provider to create an ActiveX Data
Objects (ADO) recordset that uses a lock type of adLockBatchOptimistic, when the
recordset performs a query that returns a single record from a large table, the
query may take a long time to complete. Creating an index on the field in the
WHERE clause of the query can improve performance, but not significantly.

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for Visual FoxPro for
Windows 7.0. For additional information, please see the following article in the
Microsoft Knowledge Base:

  Q316964 How to Obtain the Latest Visual FoxPro for Windows 7.0 Service Pack

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Visual FoxPro for
Windows 7.0. This problem was first corrected in Visual FoxPro for Windows 7.0
Service Pack 1.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

To reproduce the behavior, run the following code. The code creates a large
FoxPro table and then queries the table using the Visual FoxPro 7.0 OLE DB
Provider. Although the query returns only a single record, it takes a long time
to complete.

  *!* Comment the 2nd #DEFINE and uncomment the first
  *!* to see increased performance.
  *!* #DEFINE LOC_LockType 1 && adLockReadOnly
  #DEFINE LOC_LockType  4 && adLockBatchOptimistic

  LOCAL loConn AS ADODB.CONNECTION, ;
  	loRS AS ADODB.Recordset, ;
  	lnStartTime AS NUMBER, ;
  	lnTotalTime AS NUMBER, ;
  	lnLooper AS INTEGER

  CD JUSTPATH(SYS(16))
  CLOSE DATA ALL
  IF !FILE('GreatBigTable.DBF')
  	WAIT WINDOW "Creating and populating table..." NOCLEAR NOWAIT
  	CREATE TABLE 'GreatBigTable.DBF' (EID I NOT NULL, ;
  		NUM I NOT NULL, ;
  		PYEAR I NOT NULL, ;
  		ESTATU C(2) NOT NULL, ;
  		ECODE I NOT NULL, ;
  		DDATE D NOT NULL, ;
  		DDATET T NOT NULL, ;
  		TYPEC C(1) NOT NULL, ;
  		PLAN I NOT NULL, ;
  		OPTION I NOT NULL, ;
  		EOI L NOT NULL)

  	FOR lnLooper = 1 TO 1000000
  		INSERT INTO GreatBigTable VALUES(lnLooper, ;
  			lnLooper, ;
  			lnLooper, ;
  			"CA", ;
  			lnLooper, ;
  			DATE() + lnLooper, ;
  			DATETIME() + lnLooper, ;
  			"X", ;
  			lnLooper, ;
  			lnLooper, ;
  			.T.)
  	ENDFOR
  	USE IN SELECT("GreatBigTable")
  	WAIT CLEAR
  ENDIF

  lnStartTime = 0
  lnEndTime = 0
  loConn = CREATEOBJECT("ADODB.Connection")
  loRS = CREATEOBJECT("ADODB.RecordSet")

  loConn.OPEN("PROVIDER=vfpoledb.1;DATA SOURCE=" + JUSTPATH(SYS(16)))

  WITH loRS
  	.CursorType = 3 && adOpenStatic
  	.CursorLocation = 3 && adUseClient
  	.LockType = LOC_LockType
  	lnStartTime = SECONDS()
  	WAIT WINDOW "Query is running..." NOWAIT NOCLEAR
  	.OPEN("Select * from GreatBigTable where EID= 178441", loConn)
  	lnTotalTime = SECONDS() - lnStartTime

  	WAIT CLEAR
  	MESSAGEBOX(TRANSFORM(.RecordCount) + " record return in " + ;
  		TRANSFORM(lnTotalTime) + " seconds.")
  ENDWITH

  loRS.CLOSE
  loConn.CLOSE
  RELEASE ALL

Additional query words: OLEDB kbVFP700sp1fix

======================================================================
Keywords          : kbGrpDSFox kbDSupport kbCodeSnippet kbvfp700 _IK283 
Technology        : kbVFPsearch kbAudDeveloper kbVFP700
Version           : :7.0
Issue type        : kbbug
Solution Type     : kbfix

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